Pressure control



Feb. 28, 1967 &

N. R. HAGLER PRESSURE CONTROL Filed March 2, 1964 IN VENTOR. 770/7220?) fi H y/er BY a M United States Patent 3,306,214 PRESSURE CONTROL Norman R. Hagler, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. 2, 1964, Ser. No. 348,680 4 Claims. (Cl. 10342) My invention is directed to control or regulation of the outlet pressure of a pump and is particularly directed to apparatus having a consistent response to the average pressure output value of a pump having a pulsating delivery characteristic.

In its preferred embodiment, my invention includes a relief valve connected between the outlet or discharge port and the inlet or intake port of a pump having a reciprocating diaphragm or piston or other structure which delivers a liquid under rapidly and widely varying pressure and flow. The regulating device is constructed so as to average out the pulsations of pressure and thus maintain a delivery pressure which is not greatly influenced by the cyclic transients in the pump discharge.

The invention as described here is embodied in a fuel pump of the reciprocating diaphragm type. Such pumps have many advantages in simplicity, economy, and reliability, but a pump of this sort delivers fluid only during one direction of movement of the diaphragm, \It thus delivers no fluid during half of the pump cycle and fluid at widely varying flow rates (depending upon the actuating means for the diaphragm) during the other half of the cycle. In a pump to supply fuel to a gas turbine engine these pulsations have an undesirable effect on the valve of the relief type controlling or limiting the pump dis charge pressure. My invention involves means for averaging out the pulsations of pump discharge pressure applied to the relief valve so that its action is smooth and consistent and cyclical opening and closing of the valve in response to individual strokes of the diaphragm is eliminated.

The nature of the invention and its advantages will be apparent to those skilled in the art from the succeeding detailed description of the preferred embodiment shown in the accompanying drawings.

FIGURE 1 is a plan view of a fuel pump embodying the invention.

FIGURE 2 is a partial the plane indicated by the sectional view of the same on line 22- in FIGURE 1.

FIGURE 3 is a partial sectional view of the same on the plane indicated by the line 33 in FIGURE 1.

The pump illustrated includes a body 6 made of a number of stacked sections including a 'base 7 shown fragmentarily in FIGURE 3, a plunger guide plate 8, an inlet ring 9, a main pump body 11, a plate 12, a main valve body 13, and a cover plate 14. The parts 9' to 14 are held assembled by machine screws 16 which extend into the guide plate 8. The pump is actuated by a rod or plunger 17 reciprocating in a bushing in the guide 8. In the preferred embodiment of the invention, the plunger 17 is reciprocated by an eccentric and connecting rod mechanism, the eccentric being on a drive shaft mounted in the portion 7 of the body. Since the details of the mechanism for reciprocating the plunger '17 are immaterial, they are not shown. Plunger 17 engages a sealing diaphragm 19 held between the parts 8 and 9, and through the diaphragm 19 and a spacer 21 reciprocates a second diaphragm 22 mounted above diaphragm 19 and held between the margins of pump body portions 9 and 11. A pumping chamber 23 is defined Within the body portion 11 above diaphragm 22. An inlet check valve 24 is mounted on the diaphragm and an outlet check valve 26 is mounted on the shoulder Patented Feb. 28, 1967 27 at the upper end of chamber 23. Fuel is admitted to the pump through a line 28 into a space 29 within the pump body 11 from which it flows through a passage 31,

defined in part by an aperture in diaphragm 22, into the pump inlet chamber 33 within the body portion 9 between the two diaphragms. The fuel discharged by the pump flows through check valve 26 into a space 34 in the upper part of body 11 from which it fiows into the pump outlet line 35.

The upper end of chamber 34 is closed by valve plate 12 which defines an opening 36 which is the inlet to a relief valve. Gaskets 37 and 38 are disposed between plate 12 and the pump body 11 and valve body 13, respectively. The relief valve includes a hollow movable valve member or stem 40, the lower end of which seats against the plate 12 around the opening 36. This valve stem is guided in a bushing 41 in the valve body 13 and has a shoulder which bears against the pressure responsive diaphragm 42 through a washer 43. A spring retainer- 44 held by nut 46 fixes the diaphragm to the stem 40. The cap 14 includes a dome portion 47 which serves as a retainer for a compression spring 48 which bears against the diaphragm to bias the stem 40 to the valve closed position. The diaphragm 42 has a thickened margin 51 retained in an annular recess 52 in the top of valve body 13 by cover plate 14. A recess in the upper surface of the valve body 13 defines a liquid chamber 54 below diaphragm 42 and the space above the diaphragm under the cap 14 is vented to atmosphere at 56.

Recess 57 in the lower surface of valve body 13 communicates through an opening 58 in plate 12 with the pump inlet space 29. The interior of the hollow stem 40 is always in communication through opening 36 with the pump discharge chamber 34. -It connects through restricted lateral ports 61 with the chamber 54 under diaphragm 42. As will be apparent, the pressure from pump outlet chamber 34 transmitted through the valve stem to chamber 54 will lift the valve stem and open the relief valve when the pressure thus exerted on diaphragm 42 overcomes the resisting force of spring 48. Even though pulsations in the discharge pressure are largely smoothed out at the fuel control or other point to which the fuel is delivered, pulsations immediately at the outlet of the pump will be quite substantial and, with the structure so far described, the relief valve would respond to the maximum pressure during each outlet pulse. This would be undesirable, since the means or average value of discharge pressure is the significant quantity.

My invention provides for response of this sort by connecting an air dome or accumulator 64 to the valve chamber 54. The bell or dome 64 constitutes an impervious chamber and has a neck 66 at its lower end having tapered threads which are received sealingly in a threaded socket 67 in the valve body. The mouth of the receiver is connected through a passage 68 in the valve body to chamber 54. The accumulator 64 is initially full of air. With a pump pressure in the range of approximately one atmosphere gauge the receiver fills approximately half full of fuel when the pump is in operation, the upper half being filled with air and vapor at twice atmospheric pressure absolute. The gas is readily compressible, and since the area of ports 61 is very small compared to the air volume in the receiver, the relatively small inflow and outflow during the port cycle of the pump will not greatly affect the pressure in chamber 54. The pressure rises slightly during the pump discharge stroke and drops slightly during the pump intake stroke, but the radical pulsations are largely filtered 0r damped out so far as the relief valve is concerned. Any persisting change in average pump discharge pressure will, however, soon bring the pressure in chamber 54 to the same value.

1. The combination of a liquid pump having a pulsating 10 delivery characteristic and a delivery connection, and a pressure controlling device connected to the outlet of the pump,

the pressure controlling device including a valve connected to the pump by a conduit and operable to control the delivered pressure,

a movable wall operatively connected to the valve,

a chamber adapted to contain liquid under pressure to exert a valve actuating force on the movable wall,

means defining a restricted connection between the outlet of the pump and the said chamber branching from the delivery connection and branching from the said conduit between the pump and the said valve,

and an elastic accumulator for fluid openly connected to the said chamber,

the area of the restricted connection being very small relative to the capacity of the accumulator so that flow through the restricted connection during a cycle of pulsation of the pump does not substantially vary the pressure in the chamber.

2. A combination as recited in claim 1 in which the valve is a relief valve.

3. The combination of a liquid pump having a pulsating delivery characteristic and a delivery connection, and a pressure controlling device connected to the outlet of the pump,

the pressure controlling device including a valve connected to the pump by a conduit and having a seat and a stem movable from the seat to control the delivered pressure,

a movable wall operatively connected to the valve stem,

a chamber adapted to contain liquid under pressure to exert a valve actuating force on the movable wall,

means defining a restricted connection through the seat and the stem of the valve between the outlet of the pump and the said chamber branching from the delivery connection and branching from the said conduit between the pump and the said valve,

and an elastic accumulator for fluid openly connected to the said chamber,

the area of the restricted connection being very small relative to the capacity of the accumulator so that fiow through the restricted connection during a cycle of pulsation of the pump does not substantially vary the pressure in the chamber.

4. The combination of a liquid pump having a pulsating delivery characteristic and a delivery connection, and a pressure controlling device connected to the outlet of the pump,

the pressure controlling device including a valve connected to the pump by a conduit and operable to control the delivered pressure,

a movable wall operatively connected to the valve,

a chamber adapted to contain liquid under pressure to exert a valve actuating force on the movable wall,

means defining a restricted connection between the outlet of the pump and the said chamber branching from the delivery connection and branching from the said conduit between the pump and the said valve,

and a gas-containing accumulator for liquid openly connected to said chamber,

the area of the restricted connection being very small relative to the capacity of the accumulator so that flow through the restricted connection during a cycle of pulsation of the pump does not substantially vary the pressure in the chamber.

References Cited by the Examiner UNITED STATES PATENTS 1,897,292 2/1933 Babitch 103224 2,214,922 9/1940 Ericson 230236 2,413,035 12/1946 De Lancey 230-22 2,764,103 9/ 195-6 Mercier 103223 2,779,290 1/1957 Wiegers 103224 2,891,626 6/1959 Szydlowski 6039.28 2,942,550 6/1960 Carter 103-42 2,950,684 8/1960 Bauerlein et al 230-236 2,971,470 2/1961 Wein et al. 103-42 MARK NEWMAN, Primary Examiner.

MARTIN P. SCHWADRON, Examiner.

W. I. KRAUSS, Assistant Examiner. 

1. THE COMBINATION OF A LIQUID PUMP HAVING A PULSATING DELIVERY CHARACTERISTIC AND A DELIVERY CONNECTION, AND A PRESSURE CONTROLLING DEVICE CONNECTED TO THE OUTLET OF THE PUMP, THE PRESSURE CONTROLLING DEVICE INCLUDING A VALVE CONNECTED TO THE PUMP BY A CONDUIT AND OPERABLE TO CONTROL THE DELIVERED PRESSURE, A MOVABLE WALL OPERATIVELY CONNECTED TO THE VALVE, A CHAMBER ADAPTED TO CONTAIN LIQUID UNDER PRESSURE TO EXERT A VALVE ACTUATING FORCE ON THE MOVABLE WALL, MEANS DEFINING A RESTRICTED CONNECTION BETWEEN THE OUTLET OF THE PUMP AND THE SAID CHAMBER BRANCHING FROM THE DELIVERY CONNECTION AND BRANCHING FROM THE SAID CONDUIT BETWEEN THE PUMP AND THE SAID VALVE, AND AN ELASTIC ACCUMULATOR FOR FLUID OPENLY CONNECTED TO THE SAID CHAMBER, THE AREA OF THE RESTRICTED CONNECTION BEING VERY SMALL RELATIVE TO THE CAPACITY OF THE ACCUMULATOR SO THAT FLOW THROUGH THE RESTRICTED CONNECTION DURING A CYCLE OF PULSATION OF THE PUMP DOES NOT SUBSTANTIALLY VARY THE PRESSURE IN THE CHAMBER. 